The present invention relates to liquid filtration apparatus and, more particularly, to structure providing an improved seal for preventing leakage past the sides of a moving filter media into an underlying liquid recovery compartment which is maintained at sub-atmospheric pressure.
Among the filtration systems commonly used to remove contaminants from liquids for recyling in machine tool operations are those employing endless chain conveyors which move through a tank to which contaminated liquid is supplied for filtration through a liquid-permeable filter media. Contaminants are deposited on the surface of the media as the liquid passes through, resulting in a bed or "cake" of contaminants which is removed either by scraping it from a stationary media by movable scraper elements, or by attaching the media to the movable conveyor belt which is continuously or periodically moved to position a fresh portion of media in the tank to perform the filtration operation.
The conveyor and media travel over an opening in the bottom of the tank beneath which is a chamber for collecting the filtered or "clean" liquid which is pumped back to the work area for reuse. Rather than relying upon an unacceptably slow rate of filtration provided by gravitational flow of the liquid through the media at a pressure differential due only to the head of liquid in the tank, the liquid collection chamber is maintained at sub-atmospheric pressure. In this way, the liquid is drawn through the media at a much faster rate without sacrificing filtration efficiency, assuming that an effective seal is provided along the edges of the media to prevent unfiltered liquid from migrating into the liquid collection chamber. U.S. Pat. No. 4,137,169, commonly owned with the present application, discloses filtration apparatus including means for effecting the aforementioned seal along the edges of the media. It has been found, however, that the seal provided by the apparatus disclosed in this patent, as well as other prior art sealing apparatus, is not always fully effective in preventing leakage along the sides of the media.
Accordingly, the principal object of the present invention is to provide liquid filtration having novel and improved means for preventing leakage of unfiltered liquid which may carry solid contaminants around the edges of a movable filter media into an underlying liquid collection chamber which is maintained at sub-atmospheric pressure.
A further object is to provide a novel and improved seal between stationary and movable portions of liquid filtration apparatus.
Other objects will in part be obvious and will in part appear hereinafter.